3 Fundamentals of press design

Blanking processes
x S = 66. 6 (s ame value as with a),a sthe same ya − xis)
l
yS
=
⋅ b + l ⋅ b + l
l
⋅ b + l ⋅ b + l ⋅ b + l ⋅ b + l
+ l + l + l + l + l + l + l
⋅ b + l ⋅b
y
y
S
S
5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12
5 6 7 8 9 10 11 12
62. 83⋅ 20+ 62. 83⋅ 20+ 94. 25⋅ 50. 9+ 60⋅ 70+ 90⋅ 45+ 80⋅ 90+ 90⋅ 45+ 80⋅0 =
62. 83+ 62. 83+ 94. 25+ 60+ 90+ 80+ 90+ 80
= 43. 25
⇒ Center of gravity S ( 66. 6; 43. 25)
in the coordinate system c.
R
This point corresponds to the point calculated using the perimeters.
Blanking clearance between punch and female die
The blanking forces ascertained on the basis of the equations provided
here assume that the correct blanking clearance has been selected
between the punch and the female die. The precise size of the blanking
clearance u [mm] depends on the thickness of the sheet metal and its
tensile and shearing strength, as well as on the blanking speed, the type
of blanking plate perforation (with or without clearance angle �[°]) and
the required quality of the cut surface (Fig.4.5.12). A larger blanking
a
b
a 3
y y
3
a a 6
a
=
3
Fig. 4.5.11 Example to determine the surface center of gravity S R:
a part to be produced
b determination using lengths of the perimeters
c determination using line centers of gravity
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
b
b 3
b
b 7
b
a 7
7
6
a
l=l 6
l
l 7
l
l
l
b
l
b
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